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<html>
  <head>
    <meta charset='utf-8'>
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    <meta name='mobile-web-app-capable' content='yes'>
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    <link rel='stylesheet' href='../css/common.css'>

    <title>Interrupted AR</title>
  </head>
  <body>
    <header>
      <details open>
        <summary>Interrupted AR Session</summary>
        <p>
          This sample demonstrates how to use an 'immersive-ar' XRSession to
          present a simple WebGL scene to an transparent or passthrough XR
          device. The logic is largely the same as the corresponding VR sample,
          with the primary difference being that no background is rendered and
          the model is scaled down for easier viewing in a real-world space.
          <a class="back" href="./">Back</a>
        </p>
      </details>
    </header>
    <script type="module">
      import {WebXRButton} from '../js/util/webxr-button.js';
      import {Scene} from '../js/render/scenes/scene.js';
      import {Renderer, createWebGLContext} from '../js/render/core/renderer.js';
      import {SkyboxNode} from '../js/render/nodes/skybox.js';
      import {InlineViewerHelper} from '../js/util/inline-viewer-helper.js';
      import {Gltf2Node} from '../js/render/nodes/gltf2.js';
      import {QueryArgs} from '../js/util/query-args.js';

      // If requested, use the polyfill to provide support for mobile devices
      // and devices which only support WebVR.
      import WebXRPolyfill from '../js/third-party/webxr-polyfill/build/webxr-polyfill.module.js';
      if (QueryArgs.getBool('usePolyfill', true)) {
        let polyfill = new WebXRPolyfill();
      }

      // XR globals.
      let xrButton = null;
      let xrImmersiveRefSpace = null;
      let inlineViewerHelper = null;

      // WebGL scene globals.
      let gl = null;
      let renderer = null;
      let scene = new Scene();
      let solarSystem = new Gltf2Node({url: '../media/gltf/space/space.gltf'});
      // The solar system is big (citation needed). Scale it down so that users
      // can move around the planets more easily.
      solarSystem.scale = [0.1, 0.1, 0.1];
      scene.addNode(solarSystem);
      // Still adding a skybox, but only for the benefit of the inline view.
      let skybox = new SkyboxNode({url: '../media/textures/milky-way-4k.png'});
      scene.addNode(skybox);

      function initXR() {
        xrButton = new WebXRButton({
          onRequestSession: onRequestSession,
          onEndSession: onEndSession,
          textEnterXRTitle: "START AR",
          textXRNotFoundTitle: "AR NOT FOUND",
          textExitXRTitle: "EXIT  AR",
        });
        document.querySelector('header').appendChild(xrButton.domElement);

        if (navigator.xr) {
          // Checks to ensure that 'immersive-ar' mode is available, and only
          // enables the button if so.
          navigator.xr.isSessionSupported('immersive-ar').then((supported) => {
            xrButton.enabled = supported;
          });

          navigator.xr.requestSession('inline').then(onSessionStarted);
        }
      }

      function onRequestSession() {
        // Requests an 'immersive-ar' session, which ensures that the users
        // environment will be visible either via video passthrough or a
        // transparent display. This may be presented either in a headset or
        // fullscreen on a mobile device.
        return navigator.xr.requestSession('immersive-ar')
            .then((session) => {
              xrButton.setSession(session);
              session.isImmersive = true;

              // Actually pass along the session start after 5 seconds.
              setTimeout(() => { onSessionStarted(session); }, 5000);

              // Throw an exception in the meantime.
              throw new Exception('Simulated Error');
            });
      }

      function initGL() {
        if (gl)
          return;

        gl = createWebGLContext({
          xrCompatible: true
        });
        document.body.appendChild(gl.canvas);

        function onResize() {
          gl.canvas.width = gl.canvas.clientWidth * window.devicePixelRatio;
          gl.canvas.height = gl.canvas.clientHeight * window.devicePixelRatio;
        }
        window.addEventListener('resize', onResize);
        onResize();

        renderer = new Renderer(gl);

        scene.setRenderer(renderer);
      }

      function onSessionStarted(session) {
        session.addEventListener('end', onSessionEnded);

        if (session.isImmersive) {
          // When in 'immersive-ar' mode don't draw an opaque background because
          // we want the real world to show through.
          skybox.visible = false;
        }

        initGL();

        session.updateRenderState({ baseLayer: new XRWebGLLayer(session, gl) });

        let refSpaceType = session.isImmersive ? 'local' : 'viewer';
        session.requestReferenceSpace(refSpaceType).then((refSpace) => {
          if (session.isImmersive) {
            xrImmersiveRefSpace = refSpace;
          } else {
            inlineViewerHelper = new InlineViewerHelper(gl.canvas, refSpace);
          }
          session.requestAnimationFrame(onXRFrame);
        });
      }

      function onEndSession(session) {
        session.end();
      }

      function onSessionEnded(event) {
        if (event.session.isImmersive) {
          xrButton.setSession(null);
          // Turn the background back on when we go back to the inlive view.
          skybox.visible = true;
        }
      }

      // Called every time a XRSession requests that a new frame be drawn.
      function onXRFrame(t, frame) {
        let session = frame.session;
        let refSpace = session.isImmersive ?
                         xrImmersiveRefSpace :
                         inlineViewerHelper.referenceSpace;
        let pose = frame.getViewerPose(refSpace);

        scene.startFrame();

        session.requestAnimationFrame(onXRFrame);

        scene.drawXRFrame(frame, pose);

        scene.endFrame();
      }

      // Start the XR application.
      initXR();
    </script>
  </body>
</html>
